Echinacea species represent the most widely used botanical in the United States herbal market. These products vary considerably with respect to the species used, the plant part, and the formulation. Since these different products can have distinctly different chemistries, it would be expected that they would exhibit different pharmacological effects. This level of complexity most likely contributes to the problem of interpreting clinical trials performed to date on these different preparations. It also underscores the importance of identifying the clinically relevant compounds within the different preparations so that standardized consistent products could be produced for the consumer market and for use in clinical trials.Strong preliminary evidence is presented that unknown compounds, extractable with organic solvents, exist within Echinacea species that are potent activators, enhancers and suppressors of monocyte function. Determining the relevance of these compounds to the therapeutic efficacy of Echinacea material will ultimately lead to the development of optimized and more appropriately standardized products. In the longterm, this research could more directly influence human health by providing information on the types of Echinacea products most appropriate for specific health concerns. These compounds will be characterized, and their relevance to the pharmacological activity of Echinacea determined, as follows: 1. A human monocyte test system, employing a luciferase reporter gene driven by NF-kappa B sequences, will be used to guide the characterization of the compounds responsible for these three activities. 2. Cloned E. angustifolia plants (propagated in vitro) will be selected for predominant expression of only one of these activities. This will facilitate isolation since they represent a consistent and unlimited source of material. 3. Determine whether the extract's ability to modify monocyte activation correlates with the levels of these newly characterized compounds within the various plant parts of E. angustifolia, E. purpurea, and E. pallida.